Art of sewing



N v- 23, 1948 J. P. #REDERICKSEN 2,454 77 ART OF SEWING- Filed June 27, 1946' Zia/9721607 A Jzmesflfiedericifsezz Patented Nov. 23, 1948 ART OF SEWING James P. Fredericksen, Braintree, Mass, assignor to United Shoe Machinery Corporation, Flemington, N. 3., a corporation of New Jersey Application June 27, 1946, Serial No. 579,713

9 Claims. 1 v

The present invention relates to the sewing of heavy leather and like substances, particularly adapted among other puropses for advantageous use in the machine manufacture of shoes.

The object of the invention is to provide a practical production method of inserting a seam connecting shoe parts or other articles composed of stiff, leather-like substances, which seam has greater compatibility with the leather than seams of waxed threads heretofore employed and, in the attainment of these results, beneficial effects are obtained by taking advantage of the fact that a glue or other similar hardened adhesive has an inherent tendency to crack and form crevices as a result of contraction while hardening and during subsequent fiexure. Crevices in a surface coating composed of cracked glue enable thread so treated to retain sufficient flexibility for uniform manipulation and easy insertion of a tight seam by machine methods of thread handling. Crevices in such coating also provide an opportunity for substantial absorption of water or other solvent to the inner fibers of the treated thread, imparting to the coating a lubricating quality and providing a sufficient supply of solvent in continuous contact with the coating as the thread is carried to the sewing point to insure eventual activation of the entire coating. While the invention is hereinafter described as'being practiced with a glue coated thread, other adhesives and solvents or softening agents may also be employed to advantage within the scope of the invention hereinafter described and claimed.

The invention consists in these and other novel features hereinafter more fully disclosed in their various aspects in connection with the following specification, claims and accompanying drawings, in which Fig. 1 is a view in sectional side elevation, i1lustrating' the principal parts of a shoe sewing machine in which a method comprising a feature of the present invention is practiced, this figure showing on a much larger scale portions of thread employed in the machine, indicating changing conditions of the thread as it progresses through the machine;

Fig. 2 is an enlarged cross-sectional view of a chain-stitch seam inserted by the machine of Fig. 1;

Fig. Sis an enlarged cross-sectional view of a glue coated thread just before it enters a shoe sewing machine; and

Fig. 4 is a similar view of the thread, illustrating its condition after formation of a seam.

According to prior practices, application of plication of glue.

water-insoluble wax compounds to a shoe sewing thread just as the thread enters a sewing machine has been found to provide effective lubrication of the thread and to impart resistance in the thread against the growth of destructive bacteria. Waxes also have an adhesive quality which assists in sealing sewing thread in place, at least for a short time after a seam is inserted. When a wax compound is hardened, however, it becomes extremely brittle and is transformed readily into fine powdery particles as a result of flexure or impact. As soon as the compound is broken up, much of its beneficial action in resist- ,ing bacterial growth and sealing the thread in position within the shoe parts is lost. Further more, small particles of wax act as an abrasive which wears away the fibers of the thread rapidly when continued fiexure occurs, as in a shoe sole.

It has been proposed heretofore to apply glue or a similar water-soluble adhesive compound, instead of water-insoluble wax, to shoe sewing thread just before it enters a sewing machine, the water-soluble compound having a greater affinity than wax for leather or other like substances from which shoes are manufactured. The glue, also, has a tougher more durable sealing action to lock the threads of a seam in position after insertion. The application of glue in this way, however, has heretofore been unsuccessful in a sewing machine and is surrounded with many practical difiiculties. The speed at which the thread is drawn through the glue determines, in part, the amount of glue coated on the thread. Movement of thread through a sewing machine is erratic and therefore, is not conducive to a uniform ap- Due to rapid manipulation of the thread by the stitch forming devices of a shoe sewing machine, much of the surplus coating on the thread is thrown off before it reaches the work. For these reasons, it is difficult to control accurately the thickness of the coating remaining, and irregular quantities of the coating thrown'off adhere to the work and the operating parts of the sewing machine.

In applying wax or other similar water-insoluble compounds to thread, the thread is drawn through the compound and also through a closefitting stripper acting to force the wax to the inner thread fibers and to remove the surplus coating from the surface of the thread so that less will be thrown off in the subsequent stitch formation. In some instances, the compound is maintained in fluid condition by heat and all of the thread handling parts of the machine are correspondingly heated to prevent accumulations 30, and a curved hook needle 32.

of compound adhering thereto. When a wax emulsion is employed, heating is unnecessary, sufficient fluidity being obtained in the liquid phase to prevent excessive accumulations in the machine.

If an attempt is made merely to substitute glue in the place of a wax compound, it is no longer possible to maintain properly a fluid condition in the glue by heat alone, and the resistance offered by viscous glue to the passage of thread is so excessive that sewing operations are impractical. If the glue is maintained in such a liquid condition by surplus solvent that the resistance to thread passage is reduced toa practical extent, then, there will be an insufficient amount applied to the thread to obtain useful results. If the glued thread sticks'to the machine or the stripper, it is difficult to release it and much time and .thread are wasted. Furthermore, if glue is forced to the inner fibers of the thread by a stripper and such thread is thereafter hardened before being drawn into the machine, it will then be diflicult if not impossible thereafter to soften the glue with sufficient rapidity to permit performance of practical sewing operations. Also, with a glue stiffened thread, stitches cannot be formed with any degree of uniformity or set tightly in the work by machine.

In the practice of the present invention according to an important feature thereof, thread is loaded with a hardened, readily soluble glue or similar adhesive coating attached to its superficial fibers only, for use in a shoe sewing machine,

'the thread retaining its flexibility through inherent crack formation in the coating after the glue is hardened. Instead of utilizing thread thoroughly impregnated according to conventional thread treating procedure, the glue load comprises heavy external accumulations sumcient in quantity after being transformed to a liquid condition to impregnate the thread to its inner fibers either while or after hardening.

Referring to the drawings, the coating on'the thread employed is cracked into a discrete form with numerous crevices 6, the particles between which crevices form plates 8 attached to the superficial fibers of the thread. At least some of the plates 8 are of band-shape, surrounding the major portion of the thread circumference, thus binding the fibers of the thread together into a compact bundle (see Fig. 3). Such plate formation is readily accomplished by flexing the thread after the coating hardens and is conducive to ease and uniformity of thread manipulation as well as to flexibility while inserting a seam. If

these plate-like bands are of a width measured along the length of the thread approximately the same as or at least commensurate to the diameter of the thread, sharp bends in the thread during stitch formation are not resisted unduly by the coating, the thread retaining its fiexilibity until the stitches are formed regardless of the treatment given.

In utilizing the glue coated thread in asewing machine, a cop IU of. the threadis mounted upon a thread supply holder l2 of conventional form from which the thread passes over suitable guides I l, it to a solvent container I8 and to the thread engaging and manipulating devices of the stitch forming devices including a tension wheel 20, a thread guide roll 22, an auxiliary take-up 24, a main take-up 2G, a-looper 28, a thread finger As illustrated, the machine is of the type disclosed in United States Letters Patent No. 1,108,560, granted 4 August 25, 1914, upon application of Andrew Eppler, or No. 1,971,575, granted August 28, 1934, upon application of Alfred R. Morrill, or in inventors prior application Serial No. 660,233, filed April 6, 1946. The type of machine thus identified is an inseam shoe sewing machine Which is adapted to connect the lasted leather upper, leather insole and leather welt of a Goodyear welt shoe. This machine operates to insert a chain-stitch scam in such a lasted shoe 34 and to direct a Welt 36 into the seam with the chain 38 of the seam engaging the welt. Parts of the shoe through which the stitches pass are composed of stiff heavy leather requiring the use of,

beyond their breaking point without obtaining complete conformity of the parts in firm contact with each other.

Features of the invention include a method of inakingshoes in which is-used a coated thread having plate-like particles and bands of hardened soluble glue surrounding substantial proportions of its circumference, which thread before being drawn past the said thread manipulating devices of the machine is immersed in a solvent bath composed principally of cold water 40 in the container 18. In addition to the water, a plasticizing agent, as for instance glycerine, may

be added. Also, a small percentage of phenol or other preservative gives desirable results.

The solvent containerv [8 corresponds in most particulars with the ordinary wax pot of the machine, in-which there usually is provided a supply of melted or emulsified wax. The thread, as it enters the container absorbs through the crevices 6 and between its inner fibers a quantity of water, and the coating begins to soften and to be transformed into a flexible mass with a slick lubricated surface. At the same time, the coating begins to swell and to close up the crevices 0 between the glue particles attached to its outer surface. The water contained between the inner thread fibers thereafter provides an abundant supply in contact with the coating until the sewing point is reached, The mere application of cold Water, however, to the coating is not sufficient to cause the glue in the coating to become thoroughly liquified. The glue therefore will not enter the interstices between the inner fibers of the thread to any substantial extent by capillary action or cause difficulty from adhesion between the thread and the stitch forming devices of the machine.

The process of swelling the coating continues after the thread has been withdrawn from the container i0 and, in order to avoid scraping the coating off the thread as it leaves the water bath, the usual stripper is removed from the container IE to provide an opening 42 with'a substantial clearance for both the thread and coating. After 'the thread is carried past the tension wheel 20 in the thread, the major portion of the coating still retaining its position as a flexible mass on the superficial fibers. Since the glue coating swells as long as water remains in contact with it, the flexibility of the thread is unaffected by its speed of movement through the solvent container I8 or the time consumed in moving from the container to the sewing point. If the thread moves rapidly less swelling takes place but the thread retains its flexibility by reason of the softenedportions of glue in the crevices of the coating. If the thread moves slowly the swelling of the entire coating itself renders it flexible.

Upon reaching the looper and needle, the thread is rapidly manipulated and eventually drawn through close-fitting needle perforations in the work to form the chain stitches of Fig. 2. The frictional engagement of the thread caused by rapid manipulation of the needle in contact with the inner surfaces of the perforations in the shoe parts produces heat concentrated on the outer surfaces of the thread in such a manner that, in its swollen condition, a large proportion of the coating inv its flexible mass form is broken down and transformed into a liquified condition having a beneficial lubricating effect. In its broken-down liquid condition, the glue of the coating is readily forced between the inner fibres of the thread while being drawn through the needle perforations, as indicated in Fig. i, and caused to penetrate the thread completely. If any unliquefied portions of glue remain on the superficial fibers, they will be scraped off onto the engaged shoe parts, par ticularly at the outer ends of the needle perforations (Fig. 2). After each stitch is completed, the glue hardens at the outer ends of the needle perforations in the form of external deposits it which look in place the interengaging chain portions of the thread. Also, due to the glue afiinity for the substance of the leather, a rigid durable bond is obtained between the leather and the thread;

That part of the glue which is absorbed by the inner fibers ofthe thread acts when rehardened to stiffen the fibers into a stitch configuration of a particularl retentive form and rigid character, rendering the seam extremely resistant to displacement. This is the condition of the thread which exists shortly after the seam has been.

To accelerate rehardeningof'the glue and bonding of the thread and shoe parts together, the sewed shoe may be subjected to a reduced temperature. Beneficial results are also obtained by maintaining a dry atmosphere about the work during and after sewing.

Treatment of glue coated thread, according to the present invention, has still further advantages not obtained by treatment with waterinsoluble wax. The natural moisture content of the leather acts to temper the glue, preventing crack formations in the coating after sewing and giving it slight flexibility while the adhesive bond of the glue upon the thread and shoe parts is maintained. In fact, it has been found possible to eliminate entirely the use of the water bath Where the leather being sewn has a high moisture content, the frictional heat assisting in activation of the glue. The use of water soluble glue is therefore advantageous because the character of the glue more nearly matches that of the leather. Thus, even with sewed leather which is dried and hardened, the glue content of the thread in a seam is similarly hardened and, with the addition of moisture to the leather to soften it, the glue also becomes more flexible. With a flexible bond of adhesive material which is compatible with the character of the leather, a better balance in the forces exerted between the stitches and the shoe parts is maintained and less strain is applied to the interengaging and adhesively locked surfaces of the leather and thread fibers. Also, less cracking of the bond occurs than with a relatively inflexible wax.

With the use of water-insoluble wax on sewing thread, an excessive moisture content in the leather does not in any way affect the character of the wax except to reduce its afiinity for the leather. Accordingly, with increased moisture content in the leather and'a resultant greater flexibility, there is more likelihood of dislodgement between the shoe parts as a result of fracture in the wax bond between the stitches and the shoe parts. With the use of a water-soluble glue, an excessive increase of moisture in theleather may permit a shift to take place between the engag ing surfaces of the thread fibers and the shoe parts without disrupting or fracturing the bond obtained by the glue.

The application of water-soluble glue to shoe sewing thread outside of a shoe sewing machine as a separate operation prior to sewing greatly simplifies the use of the thread and avoids complications resulting from the use of heat in the machine. With an emulsified wax, it is possible to use an unheated wax pot, but the problems of maintaining the supply of wax in uncontaminated fluid condition and in keeping the wax stripper in proper adjustment requires frequent attention on the part of the operator. With glue applied to the thread outside of the machine, no supply of special thread treating compound is required in the machine and no stripper is necessary, thus relieving the operator of attention in these respects. Furthermore, the application of glue coating to the thread is made under more easily controlled conditions when divorced from the actual sewing operations, the coating being readily applied to the thread by a thread processor. Indeed, the application of such coating may conveniently be made directly after thread spinning or twisting operations, the condition of the thread being maintained more closely to the standards set up by the processor as a result. Coating at that time holds the fibers of the thread in more compact relationship and prevents displacement particularly between the superficial fibers so that, when heavy strain is eventually applied to the thread. it will be evenly distributed between the fibers. If the application and hardening of the coating are so controlled that the plate-like bands of glue each surround a substantial proportion of the thread circumference, as in Fig. 3. a marked improvement results in the shelf life of the thread without reducing its flexibility in use. Also, the thread may thereafter be flexed substantially without displacing the relationship of the fibers.

Most common types of adhesives, glues, pastes or water-soluble gums and resins may be used to advantage in thread coatings of this nature.

Glues derived fromcasein, albumin and :bone also are eifective. A water-activated glue may be employed which is transformed eventually into a water-insoluble composition bythe use of formaldehyde in the solvent container l8. It may be desirable to coat the thread, in some instances, with applications of glue in dry powdered form by pressure or by a low degree of heat.

The use of threads having a water-soluble glue Coating of the nature just referred to is particularly advantageous with synthesized plastic fibers-which are continuous and have a tendency to separate or broom as a result of frictional electrification. Certain synthetic thread. fibers also are so wiry that they willistrand on the hook of the needle during sewing'operations. A-coating of water-soluble glue overcome-s these difiiculties by binding the outer fibers of such threads securely in place.

The nature and scope of the invention having been indicated and a particular manner of carrying it out having been described, what is claimed 1s:

1. That improvement in sewing, which comprises assembling parts to be operated upon, providing a thread loaded with accumulations of hardened adhesivein discrete form to enable the thread to retain its flexibility, transforming the adhesive into a flexible mass to cause it to penetrate the thread, and inserting with the thread while flexible a seam connecting the parts to cause the thread thereafter to become rigidly bonded in place within the parts after the adhesive rehardens.

2. That improvement in methods of sewing flexibility, insertingwith the thread while flexible a seam connecting the parts and transforming the adhesive on the thread into a flexible mass to cause it thereafter to become bonded to the parts and rigidly stiffened into retentive stitch configurations when the adhesive rehardens.

3. That improvement in methods of sewing which comprises assembling parts to be operated upon, providing a thread loaded with accumulations of hardened adhesive in discrete form to enable the thread to retain its flexibility, inserting with the thread while flexible a seam connecting the parts, transforming the adhesive into a flexible mass to cause it to penetrate the thread, and thereafter causing the adhesive 'to reharden,

bonding the outer fibers of the thread to the parts.

4. That improvement in methods of sewing, which comprises assembling parts to be operated upon; providing a thread loaded with accumulations of adhesive in discrete form to enable the thread to retain its flexibility, transforming the adhesive into a flexible mass to cause it to penetrate-to the inner fibers of the thread, inserting with the thread while flexible a chain-stitch seam connecting the parts, and causing the adhesive to be liquefied and forced between the inner fibers of the thread during the insertion of the seam.

5. That improvement in methods of sewing, which comprises assembling parts to, be operated upon, providing a flexible sewing thread the outer fibers of which carry a hardened adhesive coating cracked with numerous crevices to form particles so small that:the flexibility of thethread is retained, immersing the thread in a solvent bath to cause the solvent to enter between the inner fibers through the crevices of the coating; and inserting with the thread while flexible a seam connecting the parts to cause the adhesive to be drawn through the parts and to penetrate the thread to the inner fibers thereof.

6. That improvement in methods of sewing, which comprises assembling parts to be operated upon, providing a flexible sewing thread the outer fibers of which carry a hardened adhesivecoating cracked with numerous crevices to form particles so small that the flexibility of the thread is retained, immersing the thread in a solvent bath to cause the solvent to enter between the inner fibers through the crevices, of the coating, drawing the thread rapidly through close-fitting perforations in the parts to cause liquefaction of the adhesive by frictional heat while the solvent remains in contact with the adhesive, and forming a seam connecting the parts with the liquid adhesive carrying thread.

'7. That improvement in methods of sewing, which comprises assembling parts to be operated upon, providing a flexible sewing thread the outer fibers of which carry a hardened adhesive coating cracked with numerous crevices to form particles so small that the flexibility of the thread-is retained, immersing the thread in a solvent bath to cause the solvent to enter between the inner fibers through the crevices of the coating, and inserting with the thread a seam connecting the parts by drawing the thread through perforations in the parts with suflicient rapidity to liquefy the adhesive.

8. That improvement in methods of sewing, which comprises assembling parts to be operated upon, providing a flexible sewing thread the outer fibers of which carry a hardened glue coating cracked with numerous crevices to form particles so small that the flexibility of the thread is retained, immersing the thread in a water bath to cause the water to enter between the inner fibers through the crevices of the coating, and inserting with the thread a seam connecting-the parts while the water remains in contact with the coating to cause the glue to penetrate to the parts and to the inner fibers of the thread.

9. That improvement in methods of sewing, which comprises assembling parts to be operated upon, providing a, flexible sewing thread the outer fibers of which carry a hardened glue coating cracked with numerous crevices to form particles so small that the flexibility of the thread is retained, immersing the thread in a water bath to cause the water to enter between the inner fibers through the crevices or" the coating, and inserting with the thread a seam connecting the parts by drawing the thread through perforations in the parts with suflicient rapidity to liquefy the glue.

JAlVEES P. FREDERICKSEN.

REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS Number Name Date 53,124 Day Mar. 13, .1866 197,575 Theine Nov. 27, 1877 1,729,169 La Chapelle -Sept; 24, 1929 

